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Mar 29, 2018, 10:28 AM
BigTradioman's Avatar

Another DAG But This Is A DAG 120

HI All! This is a few pictures of a new DAG 120 build by my good friend John Keats. The basic bones of the model where given to John by Richard Harris as it was something he had started but then, like we all do sometimes, put away till another day. John is very familiar with build large models and when we got this one home it really didnt seem much bigger than the DAG 60 I built in 2016/17. How wrong we where. As you will see this is a substantial model! Power is an NGH 38 four stroke. The head is home built from an alloy billet and due to the scary (to me anyway) landing characteristics in anything over a 5 mph breeze with a fixed pitch head, John has designed and built a full delta head with 2 separate 40kg 6 volt servos, that will enable the head to tilt forward to kill the lift and slow the blades down. Other methods where considered such as a Telmar Brake, or a disc brake from a 1/4 scale car etc etc, but this seemed the simplest solution. There will be 3 blades and with an anticipated all up weight of 17lbs wet, they are looking like 6ft blades made form Bass wood with a leading edge piano wire and ply laminated to the bottom off the blade and covered in LiPo heat shrink. Luckily John was the owner of AJ Blades and still has the machinery. Radio will be Futaba 14SG and R7008SB rx with Powerbox supply. Enjoy!
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Mar 29, 2018, 02:35 PM
Registered User
Looks like a robust AG to me! Nice covering, adds to a vintage look and feel.
Mar 31, 2018, 04:36 PM
John Hubbard
J Hubbs's Avatar
The ball links look bigger than the servos. Where did he get them ?
Mar 31, 2018, 05:25 PM
Registered User
5mm Rose joints can be bought from Amazon or EBay. At present the servos are 30kg standard size servos but look a little lost. I have some 50 kg servos on order. They are nearly twice the size. It is not 50 kg of power that is required it is just the physical size of the gear train that I feel more happy with, as the disk is going to be some 10 to 12 ft in diameter.

Apr 01, 2018, 04:49 PM
Registered User
106flyer's Avatar
Looking good Tim
Apr 04, 2018, 04:29 AM
BigTradioman's Avatar
This big old girl is now looking like being a ready to fly weight of 17 lbs so we need some input from RH on the dimensions for the delta plates. Thickness and diameter are going to be crucial.
Apr 09, 2018, 03:35 AM
BigTradioman's Avatar
An update on the blades. After some re calculation John has decided to go for a blade loading of 4oz. Blades will be 90mm wide and the same profile as my DAG 60, which has a loading of 6oz, made from solid Bass laminated to a birch ply bottom skin with piano wire leading edges. He is aiming to be ready for Old Warden in June.
Apr 09, 2018, 05:02 AM
Registered User
What kind of material did you use for covering? (looks like satin-finish)
Apr 09, 2018, 10:38 AM
Registered User
The covering is Solartex Antique Blue. Absolutely lovely stuff to use. A couple of little tricks I have learnt when I have covered the model I get some clean tissue soak it in cellulose thinners and go over all the covering. This causes the dye to run and gives a very even colour overall. Also hides some blemishes. The next thing is to use aerokote gloss with enough make it matt additive to give a satin finish. This also helps to keep the model clean.
Apr 10, 2018, 08:25 AM
Registered User
Thanks a lot for your advice, John.
Apr 10, 2018, 03:34 PM
BigTradioman's Avatar
Hi Eric, the problem we have is that the company, Solarfilm, has ceased to trade after 50years due to competition from China. I covered my DAG in Solartex which is really lovely stuff to work with, nice shrinkage, gasoline and methanol fuel proof, has a sort of painted linen finish. If you cut the edges with dressmakers Pinking Shears it gives a really nice scale looking half diamond edge. Hopefully someone will make a similar product.
Apr 11, 2018, 02:57 PM
Registered User
Hi Eric

This is where I get my solatex from
Apr 15, 2018, 07:42 AM
Registered User
Awesome looking Gyro, could you possibly let me have words of wisdom on building rotor blades for a large project many thanks. cheer Garth
Apr 17, 2018, 02:35 AM
BigTradioman's Avatar

Another DAG But This Is A DAG 120

Hi Garth, JK should reply to this as he has done a few big blades. He did the blades for my DAG and for Rich Elliotís big Rex. He does a calculation to get a loading figure and works from there. At the moment the largest cutter he has gives a 90 mm width and 10mm thickness. The cutter is mounted in a large and very scary router or spindle moulder. The profile is the standard reformed ClarkY. Each blade has 5 or 6 passes through the machine, a 2 man job.
For blades under around 40 inches we laminate hard balsa and Bass wood leading edge. Bass wood machines really smooth without too much break out at the end of the cut. For the bigger blanks, plus 40inch, we intend to use solid Bass wood blanks with a groove let into the leading edge for a length of piano wire. This is to get the c of g of the blade forward, like a fixed wing c of g. If the blade is not stiff enough a lamination of birch ply will be glued to the bottom of the blade with Aliphatic Resin. We are also experimenting with a food quality (thin) heat shrink covering. The piano wire trick was first used by DS many years ago and can be found on YouTube along with another series by Rich Harris on how to hand make blades. Our German buddy Harald, hand makes his blades and they are real works of art. I believe he skins them in fibreglass.
Apr 17, 2018, 08:27 AM
Registered User
Hi The wood should be with me in a few days. The only wood available in the length I require is Tulip Wood which is slightly harder than Bass wood. Regarding the piano wire, the groove will be made in the under side of the blade half way between a quarter of the chord and a third of the chord. Hopefully this will keep the balance correct which should also correspond with the centre of lift which is about 27% of the chord. Fingers crossed. John

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